Well defined primary dissociated cultures from 7-9 day old postnatally developing rat cerebellum, a specially designed culture perfusion chamber, radioligand binding, autoradiographic techniques, and high pressure liquid chromatography (HPLC) will be used to, 1) identify potential neurotransmitter and neuromodulatory substances through Ca2+ dependent, stimulus-evoked and spontaneous release from excitatory and inhibitory neurons, 2) identify, characterize and localize to cell type, binding (receptor) sites, and 3) examine the functional relationships between neuronal classes, and neurons and glial cells that may be mediated through identified binding (receptor) sites, their ligands and neuromodulatory substances. Initially this will include the investigation of the biochemical mechanisms by which ligand-receptor interations regulate, and are regulated by presynaptic release of amino acid transmitter substances. This will set the foundation for elucidation of postsynaptic events subsequent to binding of ligand and receptor, such as involvement of cyclic nucleotides (cAMP, cGMP), protein phosphorylation and phospholipid methylation events. Contingent upon the accomplishment of these aims, it will perhaps then be possible to study the pharmacology of in vitro CNS development, test the in vitro effects of new drugs on cultured CNS cells, elucidate the in vitro pharmacological properties of developing CNS representing specific disease states, and examine the role of afferent input on vitro cerebellar development. Once cell identification and separation techniques becomes more rigorous, attempts to determine the contributions of specific cell types to the composite pharmacology of the mixed cell cultures can then be made.